using System.Collections.Generic;
using System.Linq;
using Questionable.Model;
using Questionable.Model.Questing;

namespace Questionable.Data;

internal sealed class QuestChainBuilder
{
	private readonly QuestData _questData;

	private readonly Dictionary<QuestId, List<QuestId>> _descendants = new Dictionary<QuestId, List<QuestId>>();

	private readonly Dictionary<QuestId, QuestChain> _cache = new Dictionary<QuestId, QuestChain>();

	private readonly Dictionary<QuestId, QuestChainGraph> _graphCache = new Dictionary<QuestId, QuestChainGraph>();

	public QuestChainBuilder(QuestData questData)
	{
		_questData = questData;
		foreach (var (elementId2, questInfo2) in _questData.AllQuests)
		{
			if (!(elementId2 is QuestId item))
			{
				continue;
			}
			foreach (PreviousQuestInfo previousQuest in questInfo2.PreviousQuests)
			{
				if (!_descendants.TryGetValue(previousQuest.QuestId, out List<QuestId> value))
				{
					value = new List<QuestId>();
					_descendants[previousQuest.QuestId] = value;
				}
				value.Add(item);
			}
		}
	}

	public QuestChain GetChain(QuestId questId)
	{
		if (_cache.TryGetValue(questId, out QuestChain value))
		{
			return value;
		}
		List<QuestId> list = new List<QuestId>();
		CollectAncestors(questId, list, new HashSet<QuestId>());
		list.Add(questId);
		List<QuestId> list2 = new List<QuestId>();
		CollectDescendants(questId, list2, new HashSet<QuestId>());
		QuestChain questChain = new QuestChain(list, list2, questId);
		_cache[questId] = questChain;
		return questChain;
	}

	public QuestChainGraph GetChainGraph(QuestId questId)
	{
		if (_graphCache.TryGetValue(questId, out QuestChainGraph value))
		{
			return value;
		}
		HashSet<QuestId> hashSet = new HashSet<QuestId>();
		CollectAllRelated(questId, hashSet);
		Dictionary<QuestId, List<QuestId>> prerequisites = new Dictionary<QuestId, List<QuestId>>();
		Dictionary<QuestId, List<QuestId>> dictionary = new Dictionary<QuestId, List<QuestId>>();
		foreach (QuestId item in hashSet)
		{
			prerequisites[item] = new List<QuestId>();
			dictionary[item] = new List<QuestId>();
		}
		foreach (QuestId item2 in hashSet)
		{
			if (!_questData.TryGetQuestInfo(item2, out IQuestInfo questInfo))
			{
				continue;
			}
			foreach (PreviousQuestInfo previousQuest in questInfo.PreviousQuests)
			{
				if (hashSet.Contains(previousQuest.QuestId))
				{
					prerequisites[item2].Add(previousQuest.QuestId);
					dictionary[previousQuest.QuestId].Add(item2);
				}
			}
		}
		Dictionary<QuestId, int> dictionary2 = new Dictionary<QuestId, int>();
		List<QuestId> list = hashSet.Where((QuestId q) => prerequisites[q].Count == 0).ToList();
		foreach (QuestId item3 in hashSet)
		{
			dictionary2[item3] = 0;
		}
		Dictionary<QuestId, int> dictionary3 = new Dictionary<QuestId, int>();
		foreach (QuestId item4 in hashSet)
		{
			dictionary3[item4] = prerequisites[item4].Count;
		}
		Queue<QuestId> queue = new Queue<QuestId>(list);
		foreach (QuestId item5 in list)
		{
			dictionary2[item5] = 0;
		}
		while (queue.Count > 0)
		{
			QuestId key = queue.Dequeue();
			foreach (QuestId item6 in dictionary[key])
			{
				int num = dictionary2[key] + 1;
				if (num > dictionary2[item6])
				{
					dictionary2[item6] = num;
				}
				dictionary3[item6]--;
				if (dictionary3[item6] == 0)
				{
					queue.Enqueue(item6);
				}
			}
		}
		foreach (QuestId item7 in hashSet)
		{
			if (!dictionary2.ContainsKey(item7))
			{
				dictionary2[item7] = 0;
			}
		}
		int num2 = ((hashSet.Count > 0) ? dictionary2.Values.Max() : 0);
		List<List<QuestId>> list2 = new List<List<QuestId>>();
		for (int num3 = 0; num3 <= num2; num3++)
		{
			list2.Add(new List<QuestId>());
		}
		foreach (QuestId item8 in hashSet)
		{
			list2[dictionary2[item8]].Add(item8);
		}
		foreach (List<QuestId> item9 in list2)
		{
			item9.Sort((QuestId a, QuestId b) => a.Value.CompareTo(b.Value));
		}
		QuestChainGraph questChainGraph = new QuestChainGraph(prerequisites, dictionary, dictionary2, list2, questId);
		_graphCache[questId] = questChainGraph;
		return questChainGraph;
	}

	public void Invalidate()
	{
		_cache.Clear();
		_graphCache.Clear();
	}

	private void CollectAllRelated(QuestId questId, HashSet<QuestId> result)
	{
		CollectAncestorsSet(questId, result);
		result.Add(questId);
		CollectDescendantsSet(questId, result);
	}

	private void CollectAncestorsSet(QuestId questId, HashSet<QuestId> visited)
	{
		if (!visited.Add(questId) || !_questData.TryGetQuestInfo(questId, out IQuestInfo questInfo))
		{
			return;
		}
		foreach (PreviousQuestInfo previousQuest in questInfo.PreviousQuests)
		{
			CollectAncestorsSet(previousQuest.QuestId, visited);
		}
	}

	private void CollectDescendantsSet(QuestId questId, HashSet<QuestId> visited)
	{
		if (!visited.Add(questId) || !_descendants.TryGetValue(questId, out List<QuestId> value))
		{
			return;
		}
		foreach (QuestId item in value)
		{
			CollectDescendantsSet(item, visited);
		}
	}

	private void CollectAncestors(QuestId questId, List<QuestId> result, HashSet<QuestId> visited)
	{
		if (!visited.Add(questId) || !_questData.TryGetQuestInfo(questId, out IQuestInfo questInfo))
		{
			return;
		}
		foreach (PreviousQuestInfo previousQuest in questInfo.PreviousQuests)
		{
			CollectAncestors(previousQuest.QuestId, result, visited);
			if (!result.Contains(previousQuest.QuestId))
			{
				result.Add(previousQuest.QuestId);
			}
		}
	}

	private void CollectDescendants(QuestId questId, List<QuestId> result, HashSet<QuestId> visited)
	{
		if (!visited.Add(questId) || !_descendants.TryGetValue(questId, out List<QuestId> value))
		{
			return;
		}
		foreach (QuestId item in value)
		{
			if (!result.Contains(item))
			{
				result.Add(item);
			}
			CollectDescendants(item, result, visited);
		}
	}
}